https://www.visual-paradigm.com/guide/uml-unified-modeling-language/what-is-uml/ https://drive.google.com/drive/u/0/folders/0B44SX73387qCfjhKR0IwU05XRVBkeEotWWVHUFhoUzN1ZVRNNU42dXlHdkotdnN0VjlTQVU https://en.wikipedia.org/wiki/Use_case_diagram#/media/File:Use_case_restaurant_model.svg